1. Field of the Invention
The present invention is related to an oblique thread-guiding link of a sewing machine, in which the swing arm is obliquely mounted in the sewing machine.
2. Description of the Prior Art
FIGS. 1 and 2 show a conventional sewing machine. A swing arm 91 is pivotally mounted in the sewing machine. The center of the swing arm 91 has a sleeve 911 having a shaft hole 912. A pivot shaft 92 is axially fitted through the shaft hole 912. Two ends of the pivot shaft 92 are perpendicularly pivotally mounted between two sidewalls 93a, 93b of the sewing machine. A front swing arm 91a forward radially projects from a first side of the sleeve 911. A rear swing arm 91b rearward radially projects from a second side of the sleeve 911. The front swing arm 91a is positioned above a needle holder mechanism 94 and aligned and coupled therewith. The rear end of the rear swing arm 91b is positioned above a driving mechanism 95 and coupled therewith. When the driving mechanism 95 up and down drives the rear swing arm 91b, the front swing arm 91a is swung along with the rear swing arm 91b to drive the needle holder mechanism 94 to move up and down. At the same time, a thread guiding rod 96 mounted on outer side of the pivot shaft 92 is driven and swung to guide the stitch thread into the needle holder mechanism 94.
Referring to FIGS. 1 and 2, the front and rear swing arms 91a, 91b of the swing arm 91 are respectively positioned on left and right sides of the sleeve 911. Therefore, the central axis 9a of the front swing arm 91a does not coincide with the central axis 9b of the rear swing arm 91b. Instead, the axis 9a is spaced from the axis 91b by a distance D. Therefore, when the driving mechanism 95 drives the swing arm 91 to swing up and down about the pivot shaft 92, the action force F will create a bending moment M onto the swing arm 91. As a result, when the swing arm 91 quickly up and down swing, the swing arm 91 is vibrated to emit a noise. This tends to speed the wearing the pivot shaft.
It is therefore a primary object of the present invention to provide an oblique thread-guiding link of a sewing machine, including a swing arm having a front section defined as a front swing arm and a rear section defined as a rear swing arm. The center of the swing arm is formed with a shaft hole in which a pivot shaft is tightly fitted. Two ends of the pivot shaft are obliquely pivotally mounted in two opposite sidewalls of the housing of the sewing machine. One end of the pivot shaft protrudes from the housing of the sewing machine. The front end of the front swing arm is positioned above a needle holder mechanism and aligned and coupled therewith. The rear end of the rear swing arm is positioned above a driving mechanism and aligned and coupled therewith. One end of a thread-guiding fixing seat is fixedly connected with the protruding end of the pivot shaft and is driven by the swing arm to swing. A thread-guiding bar is fixed at the second end of the thread-guiding fixing seat and formed with multiple thread-guiding eyelets.
It is a further object of the present invention to provide the above oblique thread-guiding link of the sewing machine, in which the front and rear ends of the swing arm are straightly projectively positioned above the needle holder mechanism and the driving mechanism to correspondingly couple therewith. The application force point and the resistance force point are positioned on the same straight line so as to eliminate the vibration and noise produced when the swing arm swings.
It is still a further object of the present invention to provide the above oblique thread-guiding link of the sewing machine, in which two collars are respectively fitted on two ends of the pivot shaft. The bodies of the collars are inlaid in the sidewalls of the sewing machine. One end of the body of each collar is formed with a flange for abutting against inner side of the sidewall of the sewing machine. Accordingly, the pivot shaft can stably swing in a predetermined position without axially sliding.
The present invention can be best understood through the following description and accompanying drawings wherein: